Salmonella detection in dried milk products by motility enrichment on modified semisolid Rappaport-Vassiliadis medium: collaborative study

Abstract

A collaborative study involving 19 laboratories was performed to validate motility enrichment on modified semisolid Rappaport-Vassiliadis (MSRV) medium for rapid detection of motile Salmonella in dried milk products. The MSRV method was compared with the AOAC culture method for detection of Salmonella in nonfat milk powder, whole milk powder, whey powder, casein powder, and butter milk powder. Samples were artificially inoculated with Salmonella at 2 levels of contamination. Uninoculated control samples were included for each type of product. The sensitivity rates were 100% for the MSRV method and 99.0% for the AOAC culture method, while the specificity rate was 100.0% for both methods. Only for the samples of whey powder, which were inoculated with H2S negative S. tennessee, was there a significant difference in the proportion of samples positive by MSRV and the culture procedure. The MSRV method for detection of motile Salmonella in dried milk products has been adopted first action by AOAC INTERNATIONAL.